ofxBullet : Objects pass through wall/bounds

Hi !

I'm trying to use a physic world which contains objects (ofMesh plane mapped with an image).
I'm adding velocity and force to the object, but my objects are going through bounds.

Here is a video :
Video

Does anyone had the same issue and know how to solve it ?
My code is based on OfxBullet-CustomShape example, I just used ofxBulletSoftTriMesh instead of ofxBulletCustomShape, but I can post the project (Xcode), if anyone want to test it.

Thanks !

Cyril